BACKGROUNDMicrobubbles are gaining more attention in environmental, medical, agricultural and industrial processes. Alcohol addition plays an important role in controlling microbubble generation. The effect of n-butanol concentration on microbubble characteristics has not been studied, thus experiments have been done to investigate the control of microbubbles in alcohol solutions. RESULTSMicrobubbles were successfully generated using a 19-channel ceramic membrane. The bubble Sauter diameter was found to decrease with increasing n-butanol concentration. Increasing cross flow velocity and decreasing superficial gas velocity resulted in smaller bubbles. Gas holdup and specific interfacial area was found to increase with increasing n-butanol concentration. The volumetric mass transfer coefficient K(l)a was found to increase with increasing n-butanol concentration, following the trend in specific interfacial area. Increasing cross-flow velocity and superficial gas velocity resulted in increased K(l)a. CONCLUSIONSBubble characteristics in solutions with different n-butanol concentrations are very different. Alcohol addition is an important way to generate smaller bubbles and larger gas holdup. (c) 2018 Society of Chemical Industry